This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Glutamine-dependent NAD synthetase from M. tuberculosis is an important drug target. We have previously solved the structure of this enzyme by SAD. We are interest in two different type of complexes. The first are different ligand complexes of the enzyme representing discrete stable states along the reaction coordinate that will contribute to the elucidation of the regulatory mechanism of the activity at two active sites separated by 40 A and connected by an molecular tunnel. The second type of complexes are inhibitor complexes crucial to improve the design of inhibitors of this enzyme.